NLOS and reflections in harsh environment

Frequent questions asked online, offline, in forums are answered here
Post Reply
khassanov
Posts: 1
Joined: Tue May 09, 2017 3:49 pm

NLOS and reflections in harsh environment

Post by khassanov »

Hello.
It's obvious that ultrasound do not penetrate enough through walls or similar solid obstacles, and so non line of sight localization case seems not possible. But there are many other curious cases. In videos at youtube channel one holds tag with a space between it and body, tests makes in open space. But it is interesting to compare system capabilities in different environments.

Can Marvelmind Indoor “GPS” work in a presence of reflections and while NLOS to one or more beacons? For example, can I use it to localize box in storage shelf? Do other boxes and shelves break necessary conditions? Or if there is an obstacle from one side, like it may cause when mobile tag placed on a side of a box, not on top? Maybe beam can pass over shelves bars and little boxes?

Regards,
Alisher.

User avatar
admin
Site Admin
Posts: 305
Joined: Tue Jan 26, 2016 7:06 pm
Contact:

Re: NLOS and reflections in harsh environment

Post by admin »

khassanov wrote:Hello.
It's obvious that ultrasound do not penetrate enough through walls or similar solid obstacles, and so non line of sight localization case seems not possible. But there are many other curious cases. In videos at youtube channel one holds tag with a space between it and body, tests makes in open space. But it is interesting to compare system capabilities in different environments.

Can Marvelmind Indoor “GPS” work in a presence of reflections and while NLOS to one or more beacons? For example, can I use it to localize box in storage shelf? Do other boxes and shelves break necessary conditions? Or if there is an obstacle from one side, like it may cause when mobile tag placed on a side of a box, not on top? Maybe beam can pass over shelves bars and little boxes?

Regards,
Alisher.


Hello Alisher,

Usual requirement for our system is a direct line of sight to 2 or more stationary beacons at any given point you expect the localization in 2D. Or to 3 or more beacons, if you expect 3D (X,Y,Z) coordinates.

And it doesn't matter whether other beacons are NOLS. The mobile beacon must see 2 stationary ones.

However, there are many cases when this requirement doesn't necessarily hold:
- For example, on distances of up to 10-15 meters, even I completely cover the mobile beacon in my fist, the beacon is traced nearly as well as it would be completely open on the top of a helmet. The requirement of the direct line of sight doesn't go away, though. Simply, the mobile beacon is powerful enough in ultrasonic to make the ultrasonic signal to penetrate through my fist being measured by the stationary beacons
- We have tested with pretty thick fabric as well. It worked well as well. You may expect some range reduction, but, otherwise - no visible effect

Locking in storage shelf would, probably, destroy the system. but it pretty much depends on the shelf, type of the material, relative position of stationary beacons to the mobile beacon, etc. This is certainly not recommended way, but in some cases it may work too.

The worst case is when the direct path (potential line of sight) is severally blocked/attenuated/obstructed and at the same time a reflected signal from a solid wall is strong - in this case, the system may be confused.

What is recommended - to install stationary beacons so that at any point - even for very complex areas - 2 or more stationary beacons would be visible to the mobile beacon, like, on this demo video where the whole floor with complex corridors is covered: https://www.youtube.com/watch?v=4ZqyMsKGiqs&t=1s

BR,
Maxim

Post Reply